By Ashley Killough and Deirdre Walsh, CNN

(CNN) -- Scott Pruitt's controversial spending and travel decisions were the subject of a blistering congressional hearing Thursday, where the embattled administrator of the Environmental Protection Agency faced House members amid weeks of scandal.

Pruitt first testified with the House Energy and Commerce Committee and then later Thursday he will testify before the House Appropriations Committee.

While he was scheduled to talk about the budget of his agency, he's being sharply questioned from Democrats -- as well as from some Republicans -- over a long list of decisions that have landed him in the headlines. He's faced a barrage of criticism for allegedly spending extravagantly on security, building a sound proof booth in his office, approving raises for staffers and renting a condo from a lobbyist who had business before his agency.

"There are so many outstanding questions that we need truthful answers to today, because so far, we've only gotten half-truths, misleading answers, or outright falsehoods," said Rep. Frank Pallone, the top Democrat on the committee, in his opening statement.

"You are unfit to hold public office and undeserving of the public trust," he concluded.

The committee's top Republican, Chairman Greg Walden, also raised concerns that Pruitt's policies are "being undercut" by ethics controversies. "These issues are too persistent to ignore, and I know many members are looking for more clarity from you today," he said.

Pruitt addressed the allegations in his opening remarks, saying the responsibility to make changes at the EPA "rests with me and no one else" but argued much of what has been claimed is distorted.

"Facts are facts and fiction is fiction. And a lie doesn't become truth just because it appears on the front page of the newspaper," he said.

"Much of what has been targeted towards me and my team, has been half-truths, or at best stories that have been so twisted they do not resemble reality," he continued. "I'm here and I welcome the chance to be here to set the record straight in these areas. But let's have no allusions about what's really going on here."

Questions over raises

Rep. Paul Tonko, a top Democrat on the committee, was the first to question Pruitt and attempted to get the administrator to admit that he authorized the raises of two top staffers who also worked for Pruitt when he was attorney general of Oklahoma — an issue that the EPA's inspector general is also probing.

Pruitt said he was "not aware of the amount" of the raises and would not give a straight "yes" or "no" answer to whether he authorized them, but he admitted he authorized his chief of staff, Ryan Jackson, to sign off on the salary increases. Pruitt also said he was not aware that proper protocols were bypassed to issue the raises.

That was a contradiction to what he told Fox News earlier this month when he said he didn't know about the pay raises at all until they were revealed in public reports the day before the interview.

"Well then, I'm concerned that you have no idea what is going on in your name at your agency," Tonko said.

Blasting back at Democrats, Republican Rep. David McKinley argued their attempts to question Pruitt was a "classic display of innuendo and McCarthyism," adding he hoped the questions would stay focused on policy but "some just can't resist the limelight, the opportunity to grandstand."

Questions over $43,000 booth

Pruitt also addressed concerns about a $43,000 soundproof booth that his office purchased and was found to violate federal spending law by a Government Accountability Office report.

Pressed by Rep. Tony Cardenas, a California Democrat, about the booth, Pruitt said the idea originated after he received a phone call of a sensitive nature and "did not have access to secure communications."

He said he ordered his staff to address the situation. "And out of that came a $43,000 expenditure that I did not approve," he said.

Cardenas, following up, asked Pruitt if he was blaming his staff for the episode.

"Career individuals at the agency took that process through and signed off on it all the way through," Pruitt said. "I was not involved in the approval of the $43,000, and if I had known about it, Congressman, I would have refused it."

All eyes on Pruitt hearing

Key audiences at the White House and the EPA are watching Thursday's pair of hearings.

"Things are definitely grinding to a halt today," an EPA official told CNN. "I don't know of a single person planning not to stream this in their office."

Many EPA officials -- including conservative political appointees -- are hoping the EPA administrator goes up in flames, two EPA officials told CNN. Many EPA officials who believe the EPA administrator should be pushed out of his Cabinet-level position because of his behavior at the agency's helm are hoping that an abysmal televised performance will sink Pruitt in President Donald Trump's mind.

Beyond a handful of aides who are loyal to Pruitt, much of the agency's politically-appointed members have lost confidence in the EPA administrator -- believing he has been a distraction to the agency's mission and Trump's agenda.

Pruitt loyalists, though, were surprisingly upbeat Thursday morning during a senior staff meeting at EPA headquarters, one official said, appearing "extremely confident."

"They either know something nobody else does or they're that naive," one official said.

A senior White House official told CNN aides to the President will be watching Pruitt's performance, given the fact that the administrator and his team rejected White House attempts to prepare him for his testimony.

Multiple White House sources have told CNN this week that the President still backs Pruitt, though all eyes will be on his performance Thursday. At the daily White House briefing, a reporter asked spokeswoman Sarah Sanders why Pruitt still had a job in an administration that promised to "drain the swamp."

"We're evaluating these concerns, and we expect the EPA administrator to answer for them," Sanders said. "And we'll keep you posted."

Preparing for the hearing

While Pruitt turned down assistance from White House staff to prep for his hearings, he did reach out to a fellow Republican from Oklahoma for advice. "He gave me a call, and I warned him it was going to be a fairly rugged hearing," GOP Rep. Tom Cole, a senior member on the appropriations panel, told reporters Wednesday.

Cole said he told Pruitt to talk to the chairman of the committee and call individual members -- Republican and Democrat -- ahead of time. "Give them an opportunity to ask any questions they want and say 'I want to be prepared to answer anything you want to address.' I just think that puts you in a stronger position, but I have no idea whether he's done that or not," Cole added.

When asked about Pruitt opting out of a briefing by aides familiar with the committee's concerns, Cole said it was Pruitt's judgment to make. "But if you work for the President of the United States, it's usually a wise thing to listen to his direct employees."

So far at least four House Republicans have called for Pruitt to resign, though none of them sit on either committee that will question Pruitt on Thursday. Still, anticipating questions from Democrats, Cole said one could "expect a pretty highly charged hearing."

The number three House Republican, who sits on one of the panels that will question Pruitt Thursday, praised his tenure at the agency to reporters on Wednesday.

One top Democrat on the Energy and Commerce Committee, Rep. Kathy Castor, cosponsored a resolution calling for Pruitt's resignation that was signed by 170 Democratic members and senators. And several of the committee's Democrats held a news conference right before Thursday morning's hearing to highlight their concerns.

This story has been updated and will continue to update with additional developments.